Women whose father, brothers or sons are diagnosed with prostate cancer face higher odds of developing breast cancer, according to a new study.
The work by Jennifer Beebe-Dimmer, a researcher at the Barbara Ann Karmanos Cancer Institute , adds to a growing body of research into genetics or other links among cancers that at one time would have seemed unrelated.
“The more we look at cancer and the more we understand about cancer – beyond the cellular level and on a molecular and genetic level — the more we’re finding commonalities” in tumors, said Dr. Otis Brawley, chief medical officer of the American Cancer Society .
The research was published online Monday in the journal Cancer , a publication of the American Cancer Society.
If the woman has a history of both prostate and breast cancer, her odds of developing breast cancer shoot up by 78%, according to Beebe-Dimmer, who also is an associate professor at Wayne State University School of Medicine .
Brawley said the study underscores once again that the key to treating cancer is understanding what fuels it. That means treatments developed for cancer in one part of the body may be effective in tumors detected first elsewhere — a lung cancer drug, for example, that was developed for the treatment in leukemia, he said.
Researchers for years have been looking at the links between prostate and breast cancer. Both are driven by hormones – breast cancer is fueled by estrogen; prostate cancer by androgen, Beebe-Dimmer noted.
For the study, Beebe-Dimmer and co-authors examined data for 78,171 women enrolled in the Women’s Health Initiative Observational Study between 1993 and 1998.
All were free of breast cancer when they began the study. By 2009, 3,506 breast cancer cases were diagnosed in those women. Researchers homed in on those cases and the family histories associated with them.
The link between prostate cancer only and the woman’s risk of developing breast cancer is modest — a 14% boost in the overall population, according to the study.
But the presence of more than one cancer type among first-degree relatives — parents, siblings and children — significantly increases the risk. So does race.
African-American women with a family history of breast and prostate cancer in their immediate family were nearly 2 1/2 times more likely to develop breast cancer compared to African-American women without a family history of either cancer, according to researchers.
Certainly, genetic links are a possibility.
Researchers already know that mutations of BRCA1 and BRCA2 genes increase risks both in breast and ovarian cancer in women and in prostate cancer in men, although it is linked to only “a small proportion of familial clustering of these two cancers,” Beebe-Dimmer noted.
But the cause could be something else, too — that a woman and her father, brother or son share their environment and may be exposed to cancer-causing toxins, for example.
Dr. Brawley suggests several factors might be at play.
Excessive weight has been linked in studies to breast and prostate cancer. Could it be a genetic predisposition to these cancers in a family — added to a lack of exercise and poor diet — trigger cancer development? he said.
Beebe-Dimmer also notes that the clusters of cases within families might be random because both cancers “are relatively common cancers.”
The “take-home message” is this, she said: It’s important to tell your doctor about your full family history, and that includes cancers in relatives of both genders. That information could help guide decisions on when, for example, to start mammograms and other screening, she said.